The fist step is to confirm that there's nothing medically wrong, so before you do anything else just confirm with your pediatrician that it's a behavior issue that's okay to work on.
Starting there, the next step is a little counter-intuitive. You need to actually drop the subject of potty training for about a week, and totally take it off her radar. You can't reintroduce it while it's already present as something she's resistant to, so in order to push the reset button and to take a new approach you first have to stop whatever you've been unsuccessful at trying so far.
One thing you can do to help urge this along is to let your daughter pick out some big girl undies by herself: if you can get her to prefer something to the diaper, you're halfway there. We had initially let our daughter pick out some to be a reward for when she using the potty, but they turned out to be much more effective as an incentive to get started. Diapers are usually made to wick away the unpleasant sensations causes by going to the bathroom in them, as opposed to wanting to protect your new undies (and immediately being aware that something is amiss when an accident does come up).
Try to imagine going to the bathroom one way your entire life, and then being asked to change that, and you can see the difficulty a child would have grappling with this scenario. Patience from you, motivation for her, and compassionate correction when accidents happen is really the right path to getting this resolved. On the positive side, there can be a remarkable turn-around from first using the potty to being fully potty trained both day and night with a child this age--the longer you wait, the shorter it eventually takes.
